I wanted to buy from BFL clicked on payment by BitPay, copy paste address into bitcoin-qt and send.But then, I noticed that I'm firewall-ed and there is no connection with bitcoin network.After that I switched to my mobile phone connection, then some block synchronized and I though my transaction will get out but after couple of blocks I realized that mobile connection is to slow and I wont get blocks synchronized till tomorrow.I get following msg from bitpay:"Invoice Expired Your invoice has expired. Do not send any more payments to this address."

But can I stop somehow this transaction?

I have turned off bitcoin-qt.Recipient address was 1NcaC45RPmxbStkxinvqjRgxPGC8nmNMCt but there is nothing.

Is there any way to cancel transaction?Is it transmitted into network?